Debian: fix and update copyright
Debian: fix and update copyright

copyright does now follow the Debian standard format:
http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/

asmuelle/heekscnc,jihyun-kim/heekscnc,satovey/heekscnc,asmuelle/heekscnc,satovey/heekscnc,asmuelle/heekscnc,satovey/heekscnc,jihyun-kim/heekscnc,satovey/heekscnc,jihyun-kim/heekscnc,jihyun-kim/heekscnc,asmuelle/heekscnc